Mist generator

ABSTRACT

A generator is provided for producing a liquid aerosol mist of uniform dispersion characteristics that is circulated through an oxygen tent or the like. The generator includes a housing having a primary air passage therethrough which in an intermediate section is formed with an expanding venturi tube. A nebulizer is supported by the housing and functions to entrain a therapeutic liquid within a pressurized gas and subsequently to introduce the liquid-gas stream into the primary air passage upstream of the venturi tube. The expansion of the liquid-gas stream in the venturi creates a pressure differential in the passage to draw air through the same, whereby the liquid-gas stream uniformly is dispersed within the primary air stream.

United States Patent Merritt MIST GENERATOR Filed: Apr. 10, 1972 Appl.No.: 242,835

Related U.S. Application Data Continuation of Ser. No. 11,943, Feb. 17,1970, abandoned.

Field of Search ..261/1, DIG. 54, 76,

261/78 A, 116, 30, DIG. 65, DIG. 48; 1

239/102; 21/122, 123; 128/194, 188; 55/257; 259/DIG. 43

[56] References Cited UNITED STATES PATENTS Eichelman ..128/194 MerrittLester ..128/194 3,172,406 3/1965 Bird et al ..128/194 2,013,734 9/1935Prentiss... 3,104,062 9/1963 Mahon 3,278,165 10/1966 Gaffney ..259/DIG.43

FOREIGN PATENTS OR APPLICATIONS 470,089 12/1950 Canada ..261/30 PrimaryExaminerTim R. Miles Attorney-John W. Renner et al.

57 ABSTRACT A generator is provided for producing a liquid aerosol mistof uniform dispersion characteristics that is circulated through anoxygen tent or the like. The generator includes a housing having aprimary air passage therethrough which in an intermediate section isformed with an expanding venturi tube. A nebulizer is supported by thehousing and functions to entrain a therapeutic liquid within apressurized gas and subsequently to introduce the liquid-gas stream intothe primary air passage upstream of the venturi tube. The expansion ofthe liquid-gas stream in the venturi creates a pressure differential inthe passage to draw air through the same, whereby the liquid-gas streamuniformly is dispersed within the primary air stream.

6 Claims, 5 Drawing Figures PATENTED MAY 1 51975 B JMWW ATTORNEYS MISTGENERATOR This is a continuation of application Ser. No. 1 1,943, filedFeb. 17, 1970, now abandoned.

The present invention relates to a mist generator, and in particular, toa generator for producing a saturated or supersaturated aerosol mistsuitable for home and hospital therapeutic treatment.

The invention is particularly applicable to the production of arecirculated, controlled, mist atmosphere for a croup or oxygen tent,and will be described with reference thereto, although it will beapparent that the invention has other applications; for instance, in theproduction of a mist flow which can be used effectively with therapeuticmasks, in line with respirators, or other therapeutic applications.

The invention is particularly useful in combination with an atomizer ornebulizer of the type illustrated in prior U. S. Pat. No. 3,326,538issued to Marvin D. Mer ritt.

For purposes of the present application, a mist generator is defined asthat component through which a primary air stream passes, an atomizer ornebulizer being a component part of the generator and designed tointroduce an atomized or nebulized mist spray into the primary airstream.

In said prior patent, the atomizer which is defined and claimedcomprises inner and outer concentric tubes, the inner tube being closedat the bottom. Openings are provided in the sides of the tubes, theopening for the outer tube being coaxial with and slightly larger thanthe opening for the inner tube. A small stream of air is caused to beexpelled under pressure through the smaller opening of the inner tube,forcing atomized liquid from the larger opening. A reed or otherflexible member is positioned opposite the larger opening and theatomized liquid droplets are impinged against the reed causing the reedto vibrate, further reducing the droplet size.

Although the atomizer of the prior patent is broadly claimed, and isdescribed as useful for such purposes as himidifying, vaporizingmedicaments, insect spraying and vaporization of liquid fuels, it isparticularly described in combination with a carburetor for internalcombustion engines in which the atomized liquid is introduced into aprimary air stream transmitted through the carburetor.

It is an object of the present invention to provide a mist generatorparticularly suitable for therapeutic purposes in which the atomizer ofsaid prior patent can be employed.

In particular, it is an object of the present invention to provide amist generator in which the only source of motive power is compressedgas source employed in the atomizer or nebulizer.

It is further an object of the present invention to provide an improvedmist generator for producing a very fine saturated or supersaturatedmist flow suitable for use with therapeutic devices such as croup oroxygen tents, therapeutic masks, and therapeutic respirators.

It is also an object of the present invention to provide a mistgenerator for therapeutic uses in .which a variable output can beobtained.

.To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawing setting forth in detail a certain illustrativeembodiment of the invention, this being indicative, however, of but oneof the various ways in which the principles of the invention may beemployed.

In such annexed drawing:

FIG. 1 is a perspective view illustrating a croup or oxygen tent andassociated therewith a vapor generator in accordance with the presentinvention;

FIG. 2 is a detailed, enlarged, section elevation view of the vaporgenerator of FIG. ll;

FIG. 3 is an enlarged partial section view taken along line 3-3 of FIG.2 illustrating the atomizer or nebulizer in accordance with the presentinvention;

' FIG. 4 is a section view taken along line 4-4 of FIG. 2; and

FIG. 5 is an enlarged elevation section view of the atomizer ornebulizer of FIG. 3.

Referring to the drawing, in particular FIG. 1, there is illustrated acroup or oxygen tent l2 and connected therewith a mist generator 14. Theconnections between the mist generator and the tent 12 include acorrugated inlet tube 16 (inlet to the mist generator) and a corrugatedreturn tube 18, the flow of recycled air being through the two tubes,and through a nebulizer body 20 of the mist generator, connected betweenthe two tubes.

Referring to FIG. 2, the mist generator 14, in addition to the nebulizerbody 20, comprises a ninety degree inlet elbow 22, on the inlet side ofthe nebulizer body, a venturi adapter 24 on the exhaust side of thenebulizer body, a transparent plastic reservoir 26 connected beneath thebody, and an atomizer or nebulizer 28 vertically supported in the bodybetween the inlet and outlet sides thereof.

The nebulizer body 20 comprises a generally cylindrical horizontallyextending conduit 30 defining a chamber 32. It is provided with alignedupper and lower openings 34 and 36, the axes of which extend transverseto the longitudinal axis of the chamber 32 intersecting the center ofthe chamber. The upper opening 34 is embraced by an annular lip 38having in one side a downwardly extending cut-out or slot 40 (shown inFIG.3). The bottom side of the nebulizer body defines a cylindrical cap42 (which is a molded integral part of the body) embracing the loweropening 36. Internal threads 44 on the inside of the cap engage threadedsurface 46 of the reservoir 26 holding the latter in position beneaththe body.

In FIG. 2, there is shown a removable vial 48 of transparent plastic orglass positioned in the reservoir and provided with an upper flange St).The vial is held in the reservoir by clamping the flange between anupper shoulder of the threaded surface 46 of the reservoir and thebottom side of cap 42. Either the reservoir or the smaller vial can befilled with a desired therapeutic liquid. Assembled as shown, the vialis employed. If it is desired to use the larger reservoir, it is asimple matter to remove the vial. The vial may be provided with a vis'ible scale indicating the amount of liquid therein.

The venturi adapter 24 is a generally cylindrical member 52 having anend wall 54 molded integral therewith closing the end. An outlet teeconnection 56 is provided on one side of the venturi adapter close tothe wall 54, the tee connection being of lesser diameter than thecylindrical member. The end of the venturi adapter remote from the wall54 contains an insert 58, the insert extending across the mouth of theadapter to form on the downstream side thereof a chamber 60, hereinafterreferred to as a venturi chamber. The insert has a generallyfrusto-conical portion 62 within the mouth of the adapter axiallysupported therein by means of an annular radial flange 64, the smalldiameter end of the frusto-conical portion 62 being the upstream end. Aninwardly directed radial flange 66 at the upstream end defines anorifice or opening 68.

The outside surface of the venturi adapter 24 close to the upstream endthereof, in the area of insert 58, is slightly tapered permitting it tobe inserted into the downstream end of the nebulizer body 20, suchdownstream end also being slightly beveled to receive the adapter. Thetwo members are telescoped together until the nebulizer body abuts ashoulder 72 formed on the outside surface of the adapter.

Cooperating surfaces of the 90 inlet elbow and the inlet or upstreamside of the nebulizer body are also beveled in a similar manner fortelescopic insertion of the elbow open end into the body.

The atomizer or nebulizer 28 is similar to the atomizer means shown inprior U.S. Pat. No. 3,326,538. Referring to FIG. 5, the nebulizercomprises an inner tubular member 74 and concentric therewith an outertubular member 76, the inner tubular member being closed at itslowermost end 78. The outer tubular member is open at its lowermost endand connected by coupling 80 with a flexible suction tube 82 (FIG. 2)which extends downwardly from the nebulizer into either the reservoir 26or removable via] 48, whichever is employed. The suction tube terminatesin an end 84 which is provided with a stainless steel mesh filter 86.

A mounting stud 90 (FIG. 3) is threaded into the upper end of the innertubular member 74 and also is threaded into a mounting plug 92 which inturn is threaded into body 94 of the atomizer. The latter is shaped toslide downwardly into the annular lip 38 of the plastic nebulizer body,in an interference or tight fit therewith, the atomizer body 94 beingprovided with a shoulder 96 which seats on the upper surface of the lip.Both the stud and plug are hollow, as is the atomizer body accommodatingfilter 97, such body being provided with an air inlet coupling 98 whichseats into the cut-out or slot 40 on one side of the lip 38, and towhich is connected line 99 from a suitable source P of compressed gassuch as a pump, pressure tank, etc.

Referring to FIG. 5, the inner and outer tubular members 74 and 76 areprovided with aligned coaxial openings 102 and 104 in the sides thereof,the opening 104 of the outer tubular member being slightly larger indiameter than that of the inner tubular member. A flexible vibratingmember or reed 106 is suspended downwardly along the side of the outertubular member, having a flange piece 107 which is clamped between themounting plug 92 and upper end of the inner tubular member 74, as shownin FIG. 3. The distal end of the reed is axially aligned with the twoopenings 102 and 104.

It is a preferred aspect of the present invention that the generatorcomponent parts of the primary air passage are constructed of moldedpolypropylene or other suitable plastic so that the generator canreadily be disassembled, cleaned and sterilized or autoclaved. In thisway, risk of contamination is avoided and the generator can be used withdifferent medicants.

In operation, the connection 98 of the atomizer mounting body 94 isconnected with the suitable source of gas under pressure, and this gasunder pressure is admitted into the inner tubular member 74, passing ata relatively high velocity through small opening 102 of the member. Theair continues on through the larger opening 104 of the outer tubularmember, establishing a vacuum in the annular space 110 between the twomembers. This vacuum is transmitted to the flexible suction tube 82,causing liquid in either the reservoir or vial, depending upon which isused, to be drawn upwardly in the tube. The liquid is entrained in theflow of gas passing through the aligned openings 102 and 104, impingingon the head 108 of the reed 106. This causes the reed to vibrate at arelatively high frequency, dispersing the liquid in the form of a coneof very fine droplets or a mist-like cone spray into the chamber 60 ofthe venturi adapter.

As shown in FIG. 2, the flange 64 of the insert 58 supports the insertwithin the open or upstream end of the venturi adapter so that theorifice 68 of the insert is positioned about the vibrating reed 106.This causes the conical spray of liquid to pass through the venturiorifice establishing a pressure differential on opposite sides of theorifice. It is this pressure differential which may provide the solemotive force for the primary air flow from the corrugated inlet tube 16axially through the nebulizer body 20. At the same time, the venturi0rifice causes the spray to be relatively uniformly dispersed in theprimary air flow.

Referring to FIGS. 2 and 4, the insert 58 of the venturi adapter 52 isprovided along the lower side thereof with a plurality of cut-outs oropenings 112. The chamber 60 is large enough so that the heavier dropsof liquid settle out of the primary air flow and collect in the chamber.The openings 112 permit the liquid so collected to flow back into thereservoir or vial, whichever is employed.

By varying the back pressure and flow rate of the compressed gas sourceP, the mist output can be increased or reduced with regard to thepatients requirements. For instance, the intake by the patient can beincreased from a saturated flow to supersaturated simply by increasingthe pressure from the compressed gas source.

In the example of the drawings, the nebulizer is shown as connected onthe inlet side with a larger diameter tubing than on the return orexhaust side. In a particular example, the corrugated tube on the inletside can be about 2% inches in diameter, as compared with 1% inchesdiameter for the exhaust or return side tube.

If it is desired to use a smaller diameter corrugated tube on the inletside, this can be accomplished simply by using a reducing adapterconnected to the inlet side of the nebulizer body, the adapter having alarge diameter portion which telescopes into the nebulizer body inletside, and a small diameter upstream portion which connects with thecorrugated inlet tube.

The use of different sized corrugated tubing has an affect on output ofthe generator, the output with a 2 /2 inch tube being about twice thatobtained with a 1% inch tube. The size tubing seems to have littleeffect on particle size at higher pressures, although at lowerpressures, there is a greater percentage of fine droplets using thelarger diameter tubing.

Although the invention has been described with reference to a croup oroxygen tent, it should now be apparent that the invention can veryeffectively be employed with other therapeutic devices, such astracheotomy masks, aerosol masks, or laryngectomy masks where controlover velocity flow and mist out-put are easily effected to suit thepatients requirements, or with inline respirators, the amount ofhumidity desired being increased simply by adjustment of the nebulizeroutput.

It is a particular advantage of the invention, that the generator candeliver a selective output, over a very large range.

Other advantages of the invention should also be apparent. In additionto producing a very fine uniform mist spray, the generator can beoperated where the sole motive power is a relatively small capacity pumpto produce the atomizer or nebulizer air. This latter aspect isparticularly advantageous for home and hospital use. It also makes thegenerator easily movable for use with different patients, and of coursethe generator is easily cleaned and its output adjusted for such use.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A mist generator comprising a generator body having a generallyhorizontal primary air passage therethrough, a tubular nebulizerextending vertically through said primary air passage, a liquidreservoir beneath said nebulizer, said nebulizer comprising concentricinner and outer tubular portions forming inner and outer concentricchambers, axially aligned openings in said inner and outer chambers,such axis of alignment extending generally along the centerline of saidprimary air passage, the inner chamber being connected to a source ofgas under pressure while the outer chamber is in communication with saidliquid reservoir whereby gas passing through said aligned openings willdraw liquid from said reservoir and aspirate a liquid-gas stream intosaid primary air passage, a reed adapted to vibrate at high frequencymounted on said nebulizer having an inwardly projecting head thereonadapted to engage the liquid-gas stream and disperse the same into acone of very fine droplets in the primary air passage.

2. A generator as set forth in claim 1 wherein said primary air passageincludes an expanding frusto-conical venturi tube, the upstream endthereof being posi tioned about said reed on said nebulizer.

3. A generator as set forth in claim 2 wherein said primary air passageterminates in an elbow providing an enlarged chamber downstream of saidventuri tube.

4. A generator as set forth in claim 3 including a plurality of openingsin the bottom edge of said venturi tube to permit liquid to flow fromsaid enlarged chamber downstream of said venturi tube back into theliquid reservoir.

5. The generator as set forth in claim 1 wherein both ends of thegenerator body passage are in fluid communication with an oxygen tent orthe like, whereby a moisture laden gas may continually be cycled throughthe oxygen tent.

6. A mist generator as set forth in claim ll wherein the inner of saidaxially aligned openings is relatively smaller than the outer, wherebythe gas expelled through said inner opening expands in its passagethrough the outer chamber to draw the liquid from said reservoir throughthe outer opening into said primary air stream.

1. A mist generator comprising a generator body having a generallyhorizontal primary air passage therethrough, a tubular nebulizerextending vertically through said primary air passage, a liquidreservoir beneath said nebulizer, said nebulizer comprising concentricinner and outer tubular portions forming inner and outer concentricchambers, axially aligned openings in said inner and outer chambers,such axis of alignment extending generally along the centerline of saidprimary air passage, the inner chamber being connected to a source ofgas under pressure while the outer chamber is in communication with saidliquid reservoir whereby gas passing through said aligned openings willdraw liquid from said reservoir and aspirate a liquid-gas stream intosaid primary air passage, a reed adapted to vibrate at high frequencymounted on said nebulizer having an inwardly projecting head thereonadapted to engage the liquid-gas stream and disperse the same into acone of very fine droplets in the primary air passage.
 2. A generator asset forth in claim 1 wherein said primary air passage includes anexpanding frusto-conical venturi tube, the upstream end thereof beingpositioned about said reed on said nebulizer.
 3. A generator as setforth in claim 2 wherein said primary air passage terminates in an elbowproviding an enlarged chamber downstream of said venturi tube.
 4. Agenerator as set forth in claim 3 including a plurality of openings inthe bottom edge of said venturi tube to permit liquid to flow from saidenlarged chamber downstream of said venturi tube back into the liquidreservoir.
 5. The generator as set forth in claim 1 wherein both ends ofthe generator body passage are in fluid communication with an oxygentent or the like, whereby a moisture laden gas may continually be cycledthrough the oxygen tent.
 6. A mist generator as set forth in claim 1wherein the inner of said axially aligned openings is relatively smallerthan the outer, whereby the gas expelled through said inner openingexpands in its passage through the outer chamber to draw the liquid fromsaid reservoir through the outer opening into said primary air stream.